LOS ANGELES (AP) — Democrat Katie Porter captured a Republican-held U.S. House seat Thursday in the heart of what once was Southern California’s Reagan country, extending a rout of the state’s GOP House delegation that might not be over.

Porter’s upset in Orange County is a sign of changing times in a region once known nationally as a GOP fortress. The coastal county southeast of Los Angeles was home to President Richard Nixon, and President Ronald Reagan once likened it to a Republican heaven.

Porter, a law professor and protege of Massachusetts Democratic Sen. Elizabeth Warren, defeated Republican Rep. Mimi Walters, who was re-elected in a walkover just two years ago in the 45th District. The latest update to the vote count gave Porter 51 percent and a 6,203-vote lead.

Porter, 44, campaigned on an unabashed liberal agenda and in direct opposition to President Donald Trump’s priorities: She advocates overturning his tax reform package, supports universal health care, and endorses mandatory background checks on all gun sales and a ban on so-called assault-style weapons.

She said she was running “to hold Donald Trump and the powerful special interests in Washington accountable.”

In a statement Thursday, Porter said she will “bring accountability back to Washington.” She promised to protect health care and the environment, and fight for a tax system in which “everyone pays their fair share.”

A political newcomer, Porter overcame considerable odds. The district has a 7-point Republican registration edge, and Walters was re-elected in 2016 by 17 points, even though Hillary Clinton carried the district by 5 points in 2016.

The heavily suburban district was one of seven targeted by California Democrats after Clinton won them two years ago.

With Porter’s win, Democrats have picked off three GOP seats either all or partly in Orange County, and they are threatening to win another district where votes continue to be counted.

If Democrat Gil Cisneros wins that undecided race against Republican Young Kim in the 39th District where GOP Rep. Ed Royce is retiring, the county once considered Republican holy ground won’t have a GOP representative in Congress.

In returns Thursday, Cisneros climbed into a 941-vote lead, after Kim held the early lead.

Earlier, Democrat Mike Levin captured the seat long held by retiring Rep. Darrell Issa, which cuts through the southern end of the county, and Democrat Harley Rouda ousted 15-term Rep. Dana Rohrabacher in the county’s coastal 48th District. Democrats also seized GOP-held seats north of Los Angeles and in the agricultural Central Valley.

Walters, 56, was a Trump supporter and promoted the region’s economic growth under the president’s stewardship. Her campaign had labeled Porter “extreme” and out of step with the district.

The race attracted a flood of campaign dollars: Porter pulled in nearly $6 million and Walters, $4.5 million. Outside groups spent at least $11 million, according to California Target Book, which analyzes campaigns.

With Porter’s win, Democrats will hold at least a 44-9 edge in California U.S. House seats. They hold every statewide office, a supermajority in both chambers of the Legislature and a 3.7-million advantage in voter registration.